The main objective of this secondary data analysis project is to evaluate the impact of an innovative approach, Functional Family Therapy-Child Welfare (FFTCW), on the quality and costs of treatment and prevention services for substance abuse, HIV risk, delinquency, and other problem behaviors for youth and families in a child welfare setting. Child abuse and neglect are strong predictors of youth substance abuse, risky sexual behavior and conduct problems. Due to decreased funding and increased unemployment and poverty, child welfare agencies are being overwhelmed by the challenges of providing services to meet the substance abuse, HIV risk behaviors, and mental health needs of youth and families. As such, there is an urgent need to develop and test cost-efficient interventions for youth and families in child welfare settings. Research has provided support for the efficacy of family interventions for family conflict, adolescent substance use disorders, HIV-risk behaviors, and related problems. Most research has been conducted in juvenile justice or mental health settings, and there is little evidence that these interventions work in child welfare settings. The treatment costs associated with applying family interventions to all youth and families may prohibit their widespread utilization in community agencies. FFTCW was developed as a continuum of care model in which interventions are contingently applied based on the familys initial risk status. This innovative study capitalizes on significant work that has been done to develop and implement FFTCW in a real world setting; e.g., a full treatment manual and training protocol has been developed. Moreover, there is already preliminary evidence demonstrating the feasi- bility, acceptability (to providers and families), and clinical outcomes for the model. All of the training and service activities pertaining to implementing FFTCW in 5 boroughs with approximately 3000 youth and families have been funded, almost exclusively by the Administration for Childrens Services. A compari-son sample of 2000 families received services as usual (SAU) in the child welfare agency. As such, the results of this secondary analysis study would obviate the need for further treatment development of FFT (or similar family-models). FFTCW was developed with the support of a local agency and the child welfare system; the results of this study have immediate implications for the uptake and sustainability of FFTCW in real world settings. The aims of this study are: (1) To evaluate the cost and effectiveness of FFTCW compared to services as usual (SAU) in reducing adolescent substance use, HIV risk and other behavior problems, (2) To evaluate the cost and efficacy of FFTCW training on the rates of recurrent abuse, neglect, duration and out of home placement, and duration of child welfare service, and (3) To evaluate moderating and mediating effects of therapists/interventionists (fidelity), organizational (support), and family (co-occurring psychological problems) on substance abuse, HIV risk, and other problem behaviors.